The contaminated area envelops the former Mitsubishi car manufacturing site and car parts maker Monroe.

EPA

Two months after Housing SA said it would prioritise a relocation of Adelaide southern suburbs residents from a contamination zone, just one public housing tenant has moved out.

However, the government agency said eight tenants had opted to move away from Clovelly Park and it was still negotiating with the residents of a further 14 properties.

About 1,400 residents and businesses in that suburb and neighbouring Mitchell Park had been told their properties were in a wider testing zone for the chemical trichloroethylene (TCE).

Drilling was to start on Wednesday as part of testing to establish the extent of soil and groundwater contamination in the area, the site of the former Mitsubishi car manufacturing plant and car parts maker Monroe.

Concerning levels of the industrial solvent detected in soil and air in three streets in Clovelly Park prompted a recommendation that about 30 public housing tenants move away.

Environment Protection Authority (EPA) manager Richard McLachlan said the testing would try to trace the source of TCE vapour and involve drilling 137 holes across the area.

"It's actually looking at houses in particular which we've got data already for and really trying to understand where the vapour is coming from, whether it's actually from the groundwater or whether it's actually from other sources from the soil," he said.

Toxicity testing cost close to double estimate: EPA

The testing is expected to cost about $1.1 million to undertake, close to double the earlier estimate.

The EPA said that was because the analysis work was being outsourced to contractors to accelerate the process.

One of the residents now looking to move out, Justin Pearce, is buying his property.

He said he was negotiating with the SA Government about a temporary move to another house and for payment of the rent that would involve.

The results of the latest testing will not be known until December, but Mr Pearce said the damage, for him, had already been done.

"The bank has already told me if I pay off the loan and try and sell it (the house), I probably won't get the value I was hoping to get," he said.

Mr Pearce said he planned to seek compensation from the State Government.